Blacklight

Source: Wikipedia, the free encyclopedia.
For other uses, see Black Light (disambiguation).
Black light fluorescent tubes. The violet glow of a black light is not the UV light itself, but visible light that escapes being filtered out by the filter material in the glass envelope.

A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a

filter material, either on the bulb or in a separate glass filter in the lamp housing, which blocks most visible light and allows through UV,[3] so the lamp has a dim violet glow when operating.[5][6] Blacklight lamps which have this filter have a lighting industry designation that includes the letters "BLB".[3][5] This stands for "blacklight blue". A second type of lamp produces ultraviolet but does not have the filter material, so it produces more visible light and has a blue color when operating.[3][4][5] These tubes are made for use in "bug zapper" insect traps, and are identified by the industry designation "BL".[5][6]
This stands for "blacklight".

Blacklight sources may be specially designed

Robert Williams Wood, who invented the original Wood's glass
UV filters.

Although many other types of lamp emit ultraviolet light with visible light, black lights are essential when UV-A light without visible light is needed, particularly in observing

tanning beds.[4]

Medical hazard

UV-A presents a potential hazard when eyes and skin are exposed, especially to high power sources. According to the World Health Organization, UV-A is responsible for the initial tanning of skin and it contributes to skin ageing and wrinkling. UV-A may also contribute to the progression of skin cancers.[8] Additionally, UV-A can have negative effects on eyes in both the short-term and long-term.[9]

Types

Fluorescent

Two black light fluorescent tubes, showing use. The top is a F15T8/BLB 18-inch, 15-watt tube, used in a standard plug-in fluorescent fixture. The bottom is an F8T5/BLB 12-inch, 8-watt tube, used in a portable battery-powered black light sold as a pet urine detector.

Fluorescent black light tubes are typically made in the same fashion as normal

fluorescent tubes except that a phosphor that emits UVA light instead of visible white light is used on the inside of the tube. The type most commonly used for black lights, designated blacklight blue or "BLB" by the industry, has a dark blue filter coating on the tube, which filters out most visible light, so that fluorescence effects can be observed.[10] These tubes have a dim violet glow when operating. They should not be confused with "blacklight" or "BL" tubes, which have no filter coating, and have a brighter blue color.[11][10] These are made for use in "bug zapper" insect traps where the emission of visible light does not interfere with the performance of the product. The phosphor typically used for a near 368 to 371 nanometer emission peak is either europium-doped strontium fluoroborate (SrB
2F
8:Eu2+
) or europium-doped strontium borate (Sr
3B
2O
6:Eu2+
) while the phosphor used to produce a peak around 350 to 353 nanometres is lead-doped barium silicate (BaSi
2O
5:Pb+
). "Blacklight blue" lamps peak at 365 nm.[12]

Compact fluorescent (CF) black light bulb

Manufacturers use different numbering systems for black light tubes. Philips uses one system which is becoming outdated (2010), while the (German) Osram system is becoming dominant outside North America. The following table lists the tubes generating blue, UVA and UVB, in order of decreasing wavelength of the most intense peak.[a] Approximate phosphor compositions, major manufacturer's type numbers and some uses are given as an overview of the types available. "Peak" position is approximated to the nearest 10 nm. "Width" is the measure between points on the shoulders of the peak that represent 50% intensity.

Various phosphor compositions used in blacklight[a]
Phosphor
Mixture 		Peak
(
nm
) 		Width
(
nm
) 		Philips
suffix 		Osram
suffix 		U.S. Type Typical use
— 450 50 — /71 —
hyperbilirubinaemia
, polymerization
SrP
2O
7:Eu 		420 30 /03 /72 — photochemical polymerization
SrB
4O
7:Eu 		370 20 /08 /73 ("BLB")
forensics, lapidary
, night clubs
SrB
4O
7:Eu 		370 20 — /78 ("BY") [c] insect attraction, polymerization, psoriasis, tanning beds
BaSi
2O
5:
Pb
 350 40 /09 /79 "BL" [c] insect attraction, tanning beds
BaSi
2O
5:
Pb
 350 40 /08 — "BLB"
forensics
, night clubs
SrAl
11O
18:Ce 		340 30 — — — photochemistry
MgSrAl
10O
17:Ce 		310 40 — — — medical applications, polymerization
Spectrum of a black light fluorescent tube. FWHM spectral bandwidth of the 370 nm peak is about 20 nm. The tiny secondary peak (2) is light from the mercury vapor line at 404 nm leaking through the filter, which gives the lamp its purple glow.

"Bug zapper" tubes

Another class of UV fluorescent bulb is designed for use in "

electrocuted by the device. These bulbs use the same UV-A emitting phosphor blend as the filtered blacklight, but since they do not need to suppress visible light output, they do not use a purple filter material in the bulb. Plain glass blocks out less of the visible mercury emission spectrum, making them appear light blue-violet to the naked eye. These lamps are referred to by the designation "blacklight" or "BL" in some North American lighting catalogs. These types are not suitable for applications which require the low visible light output of "BLB" tubes[14]
lamps.

Incandescent

100-watt incandescent black light bulb

A black light may also be formed by simply using a UV filter coating such as

incandescent bulb. This was the method that was used to create the very first black light sources. Although incandescent black light bulbs are a cheaper alternative to fluorescent tubes, they are exceptionally inefficient at producing UV light since most of the light emitted by the filament is visible light which must be blocked. Due to its black body
spectrum, an incandescent light radiates less than 0.1% of its energy as UV light. Incandescent UV bulbs, due to the necessary absorption of the visible light, become very hot during use. This heat is, in fact, encouraged in such bulbs, since a hotter filament increases the proportion of UVA in the black-body radiation emitted. This high running-temperature drastically reduces the life of the lamp, however, from a typical 1,000 hours to around 100 hours.

Mercury vapor

mercury vapor
black light

High power

mercury vapor
black light lamps are made in power ratings of 100 to 1,000 watts. These do not use phosphors, but rely on the intensified and slightly broadened 350–375 nm spectral line of mercury from high pressure discharge at between 5 and 10 standard atmospheres (500 and 1,000 kPa), depending upon the specific type. These lamps use envelopes of Wood's glass or similar optical filter coatings to block out all the visible light and also the short wavelength (UVC) lines of mercury at 184.4 and 253.7 nm, which are harmful to the eyes and skin. A few other spectral lines, falling within the pass band of the Wood's glass between 300 and 400 nm, contribute to the output. These lamps are used mainly for theatrical purposes and concert displays. They are more efficient UVA producers per unit of power consumption than fluorescent tubes.

LED

UV LED

Ultraviolet light can be generated by some

photons
are emitted, within predominant not visible light.

Safety

See also: Subtypes of the ultraviolet spectrum

Although black lights produce light in the UV range, their spectrum is mostly confined to the longwave UVA region, that is, UV radiation nearest in wavelength to visible light, with low frequency and therefore relatively low energy. While low, there is still some power of a conventional black light in the UVB range.[15] UVA is the safest of the three spectra of UV light, although high exposure to UVA has been linked to the development of skin cancer in humans. The relatively low energy of UVA light does not cause sunburn. UVA is capable of causing damage to collagen fibers, however, so it does have the potential to accelerate skin aging and cause wrinkles. UVA can also destroy vitamin A in the skin.

UVA light has been shown to cause

sunbeds can cause DNA damage, photoaging (damage to the skin from prolonged exposure to sunlight), toughening of the skin, suppression of the immune system, cataract formation and skin cancer.[16][17]

UV-A can have negative effects on eyes in both the short-term and long-term.[9]

Uses

Ultraviolet radiation is invisible to the human eye, but illuminating certain materials with UV radiation causes the emission of visible light, causing these substances to glow with various colors. This is called fluorescence, and has many practical uses. Black lights are required to observe fluorescence, since other types of ultraviolet lamps emit visible light which drowns out the dim fluorescent glow.

Medical applications

A Wood's lamp is a diagnostic tool used in

Robert Williams Wood in 1903 using "Wood's glass", it was in 1925 that the technique was used in dermatology
by Margarot and Deveze for the detection of fungal infection of hair. It has many uses, both in distinguishing fluorescent conditions from other conditions and in locating the precise boundaries of the condition.

Fungal and bacterial infections

It is also helpful in diagnosing:

Ethylene glycol poisoning

Fluorescein glowing under ultraviolet light

A Wood's lamp may be used to rapidly assess whether an individual is suffering from ethylene glycol poisoning as a consequence of antifreeze ingestion. Manufacturers of ethylene glycol-containing antifreezes commonly add fluorescein, which causes the patient's urine to fluoresce under Wood's lamp.[21]

Other

Wood's lamp is useful in diagnosing conditions such as tuberous sclerosis[22] and erythrasma (caused by Corynebacterium minutissimum, see above).[23] Additionally, detection of porphyria cutanea tarda can sometimes be made when urine turns pink upon illumination with Wood's lamp.[24] Wood's lamps have also been used to differentiate hypopigmentation from depigmentation such as with vitiligo. A vitiligo patient's skin will appear yellow-green or blue under the Wood's lamp.[citation needed] Its use in detecting melanoma has been reported.[25]

See also

Bili light. A type of phototherapy that uses blue light with a range of 420–470 nm, used to treat neonatal jaundice.

Security and authentication

Black light is commonly used to authenticate

driver's licenses
.

Other security applications include the use of pens containing a fluorescent ink, generally with a soft tip, that can be used to "invisibly" mark items. If the objects that are so marked are subsequently stolen, a black light can be used to search for these security markings. At some amusement parks, nightclubs and at other, day-long (or night-long) events, a fluorescent mark is rubber stamped onto the wrist of a guest who can then exercise the option of leaving and being able to return again without paying another admission fee.

Biology

Fluorescent materials are also very widely used in numerous applications in molecular biology, often as "tags" which bind themselves to a substance of interest (for example, DNA), so allowing their visualization.

Thousands of moth and insect collectors all over the world use various types of black lights to attract moth and insect specimens for photography and collecting. It is one of the preferred light sources for attracting insects and moths at night. Black light can also be used to see animal excreta such as urine and vomit that is not always visible to the naked eye.

Detection of faults

Black light is used extensively in non-destructive testing. Fluorescing fluids are applied to metal structures and illuminated with a black light which allows cracks and other weaknesses in the material to be easily detected.

In addition, if a leak is suspected in a refrigerator or an air conditioning system, a UV tracer dye can be injected into the system along with the compressor lubricant oil and refrigerant mixture. The system is then run in order to circulate the dye across the piping and components and then the system is examined with a blacklight lamp. Any evidence of fluorescent dye then pinpoints the leaking part which needs replacement.

Decorative and artistic uses

Fluorescent body paint. Paints and decorations that fluoresce under black light are used in theater and several art forms.
Uranium glass glows under UV light.

It is also used to illuminate pictures painted with fluorescent colors, particularly on black velvet, which intensifies the illusion of self-illumination. The use of such materials, often in the form of tiles viewed in a sensory room under UV light, is common in the United Kingdom for the education of students with profound and multiple learning difficulties.[26] Such fluorescence from certain textile fibers, especially those bearing optical brightener residues, can also be used for recreational effect, as seen, for example, in the opening credits of the James Bond film A View to a Kill. Black light puppetry is also performed in a black light theater.

Mineral identification

Blacklights are a common tool for

rock-hunting and identification of minerals
by their fluorescence. The most common minerals and rocks that glow under UV light are fluorite, calcite, aragonite, opal, apatite, chalcedony, corundum (ruby and sapphire), scheelite, selenite, smithsonite, sphalerite, sodalite. The first person to observe fluorescence in minerals was George Stokes in 1852. He noted the ability of fluorite to produce a blue glow when illuminated with ultraviolet light and called this phenomenon “fluorescence” after the mineral fluorite. Lamps used to visualise seams of fluorite and other fluorescent minerals are commonly used in mines but they tend to be on an industrial scale. The lamps need to be short wavelength to be useful for this purpose and of scientific grade. UVP range of hand held UV lamps are ideal for this purpose and are used by Geologists to identify the best sources of fluorite in mines or potential new mines. Some transparent selenite crystals exhibit an “hourglass” pattern under UV light that is not visible in natural light. These crystals are also phosphorescent. Limestone, marble, and travertine can glow because of calcite presence. Granite, syenite, and granitic pegmatite rocks can also glow.

Curing resins

Main article: UV curing

UV light can be used to harden particular glues, resins and inks by causing a photochemical reaction inside those substances. This process of hardening is called ‘curing’. UV curing is adaptable to printing, coating, decorating, stereolithography, and in the assembly of a variety of products and materials. In comparison to other technologies, curing with UV energy may be considered a low-temperature process, a high-speed process, and is a solventless process, as cure occurs via direct polymerization rather than by evaporation. Originally introduced in the 1960s, this technology has streamlined and increased automation in many industries in the manufacturing sector. A primary advantage of curing with ultraviolet light is the speed at which a material can be processed. Speeding up the curing or drying step in a process can reduce flaws and errors by decreasing time that an ink or coating spends wet. This can increase the quality of a finished item, and potentially allow for greater consistency. Another benefit to decreasing manufacturing time is that less space needs to be devoted to storing items which can not be used until the drying step is finished. Because UV energy has unique interactions with many different materials, UV curing allows for the creation of products with characteristics not achievable via other means. This has led to UV curing becoming fundamental in many fields of manufacturing and technology, where changes in strength, hardness, durability, chemical resistance, and many other properties are required.

Other

One of the innovations for night and all-weather flying used by the US, UK, Japan and

slide rules such as the E6B
.

They may also be used to test for

LSD, which fluoresces under black light while common substitutes such as 25I-NBOMe do not.[27]

Strong sources of long-wave ultraviolet light are used in

tanning beds.[4]

See also

Footnotes

  1. ^ a b Compiled from various Philips, Osram, and Sylvania lighting catalogues.
  2. ^ a b BLB fluorescent lamps tend to run with efficiencies in the 25% range, with an example being a Phillips 40W BLB T12 lamp emitting 9.8W of UVA for 39 Watts of power input.[13]
  3. ^ a b
    calcium metasilicate
    that emits a wider band with a shorter wavelength peak at about 350 nm. These two types seem to be the most commonly used. Different manufacturers offer either one or the other and sometimes both.

References

  1. ISBN 978-1-4398-9931-1. Archived
    from the original on 2013-05-27.
  2. ISBN 978-1-4377-5581-7. Archived
    from the original on 2013-05-26.
  3. ^
    ISBN 978-0-08-086030-5. Archived
    from the original on 2013-05-27.
  4. ^
    ISBN 978-0-240-51566-3. Archived
    from the original on 2013-05-27.
  5. ^ a b c d e "Black Lights". Technical information. Glow Inc. 2010. Archived from the original on November 16, 2018. Retrieved November 15, 2018.
  6. ^ a b Rorie, Benjamin (2011). "How Do Black Lights Work?". Blog. 1000Bulbs.com. Archived from the original on February 14, 2013. Retrieved January 16, 2013.
  7. PMID 10421760. Archived
    (PDF) from the original on 2023-03-11. Retrieved 2023-01-15.
  8. ^ "Radiation: Ultraviolet (UV) radiation". World Health Organization. 9 March 2016. Archived from the original on 28 January 2021. Retrieved 15 February 2021.
  9. ^ a b "Ultraviolet (UV) protection". American Optometric Association.
  10. ^ a b "What is the difference between BL and BLB blacklights?". Specialty and Architectural Lighting. Pro Lamp Sales website. 2014. Archived from the original on 5 March 2021. Retrieved 11 December 2020.
  11. ^ "About Black Light" (PDF). Insect-O-Cutor. Archived (PDF) from the original on 2013-06-04.
  12. ^ "Osram". Photocopy and UV Emitting Phosphors / Lighting Components. Sylvania. Archived from the original on 2008-01-10 – via Archive.org.
  13. ^ "BLB LF Datasheet". philips.com. Phillips Lighting. 2018. F40T12/BLACKLIGHT/48. Archived from the original on 2018-08-29. Retrieved 2018-08-29.
  14. ^ Zaithanzauva Pachuau; Ramesh Chandra Tiwari (October–December 2008). "Ultraviolet Light- its Effects and Applications" (PDF). Science Vision. 8 (4): 128. Archived from the original (PDF) on 2015-05-06. Retrieved 2019-01-21.
  15. S2CID 29022446
    .
  16. ^ "ESPCR Blog". European Society for Pigment Cell Research. Archived from the original on 2011-07-26.
  17. ^ Zeman, Gary (2009). "Ultraviolet Radiation". Health Physics Society. Archived from the original on 2010-01-13.
  18. S2CID 42087839
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  19. ISBN 978-1-4051-6169-5. Archived
    from the original on 27 May 2013. Retrieved 14 November 2010.
  20. ^ Mike Phillips (2007-09-25). "Eikone.com". Eikone.com. Archived from the original on 2012-03-06. Retrieved 2011-11-08.
  21. PMID 2344083
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  22. PMID 17427621. Archived
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  23. S2CID 22836457.[permanent dead link
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  24. ^ Le, Tao; Krause, Kendall (2008). First Aid for the Basic Sciences—General Principles. McGraw-Hill Medical.
  25. S2CID 31548983
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  26. ^ Communication Aids for Language and Learning—UV light Archived 2010-06-05 at the Wayback Machine Equipment for use in sensory rooms for students with profound and multiple learning difficulties in United Kingdom schools.
  27. ^ The fluorometric determination of lysergic acid diethylamide and ergonovine Archived 2015-12-25 at the Wayback Machine A fluorometer was designed to detect very small amounts of LSD and ergonovine. The instrument proved less satisfactory than the Bowman fluorometer. Both LSD and ergonovine lost their fluorescence very rapidly upon strong ultraviolet irradiation. The mechanism involved in this decrease in fluorescence is not known.

External links

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